Oil well drilling procedures are well known in the art. Typically, a rotating string of drill pipe having a drill bit bores into the earth. As the bit bores deeper, additional sections of pipe are added to the string. Up until recent years, the string was typically turned by a rotary table fixed on the drilling platform. Corresponding to the requirements of the rotary table, certain standards and well known procedures for drilling were developed. With a rotary table, a long transition joint known as a kelly joint translates force from the table to the string. The string is drilled "kelly down," i.e. the length of the kelly joint, after which the kelly is withdrawn from the bore and an additional unit of drill pipe is inserted between the kelly and the string. The kelly joint, normally 42 feet long, is at least the same length as the drill pipe, typically 30 feet long.
Recent technology has introduced a vertically moveable rotary mechanism which attaches directly to the string, thereby eliminating the long kelly joint. Use of the "top drive" as it is sometimes called obviates the need for withdrawing the kelly joint each time an additional unit must be added to the string. In addition, drill pipe can frequently be added to the string in units of two or more joints, i.e. 60 or 90 feet, with a corresponding reduction in man-hours expended.
To take advantage of the potential savings of top drive systems, it is now necessary to make up double and "thribble" units of pipe while drilling. However, commercial rigs are not typically equipped to do this, and the pipe sections are made up manually using hoists and chain tongs. Frequently, the job of making up double and thribble sections of pipe cannot be done fast enough to keep up with drilling and the time savings from use of the top drive are not fully realized.
A key problem typically encountered when making up doubles and thribbles for top drive drilling is to insure proper alignment of the tool joint ends. Because derrick hoists cannot generally be positioned laterally, a reserve pipe held in a mouse hole must be angled for positioning to a joint suspended by a hoist not directly overhead. Thus, the make-up procedure cannot take advantage of gravity to obtain proper alignment. Heavy cumbersome drill pipe is difficult to handle manually. Mis-alignment can slow the job and gall the threads. Additional problems include applying a proper amount of torque using chain tongs. Usually, overall torque is measured only when the thribble is attached to the top drive unit, and there is no measurement of torque at each joint.
U.S. Pat. No. 3,293,959 to Kennard discloses a pipe-supporting well tool. The device is mounted over the rat hole on a drilling platform. A housing includes a means for supporting a length of pipe to be added to the drill string and clamping means for securing the pipe from rotation during make up with the kelly joint. The housing is mounted on spring legs such that the pipe to be made up will be resiliently supported and upwardly biased to the kelly joint. A winch having a cable and stabbing hook swings over the kelly joint and vertically aligns it with the pipe joint supported by the housing.
Other U.S. patents of interest include U.S. Pat. Nos. 3,144,085; 3,212,578; 4,290,495 to Elliston; U.S. Pat. No. 3,662,842 to Bromell; U.S. Pat. No. 1,417,490 to Brandon; U.S. Pat. No. 1,908,818 to Brown; U.S. Pat. No. 2,142,002 to Volpin; U.S. Pat. No. 2,245,960 to Claire; U.S. Pat. No. 2,321,245 to Reed; U.S. Pat. No. 4,403,666 to Willis; and U.S. Pat. No. 4,591,007 to Shaginian et al.